i think he is talking about a safebox in his house, he can control it easily if he know the combination
That's a horrible idea, what if your house is broken into and someone grabs your lockbox? you pry those things open in seconds with a crowbarI honestly believe my methods are the safest possible:
For my hot wallet I use my Trezor, for cold I use paper wallets and store them in a safe deposit box ( insured! 
)
I also keep my recovery card in my safe deposit box
)I also keep my recovery card in my safe deposit box
safe deposit box can be broken as well it's not they are immune to thieves, the big thing to have when you hold plenty of money isn't the security of it but the awareness of the people about it, in other word don't tell to anyone that you're holdin a big amount and you're safe